<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <style>
        div span{
            background-color: aqua;
        }
        div .lyt{
            font-style: italic;
            background-color: yellow;
        }
    </style>
    <title>Document</title>
</head>
<body>
    <div>
        <span class="lyt">这是div的后代标签1</span>
    </div>
    <div>
        <span class="lyt">这是div的后代标签2</span>
    </div>
    <div>
        <span>这是div的后代标签3</span>
    </div>
    <div>
        <span>这是div的后代标签4</span>
    </div>
</body>
</html>